Circuit breaker refers to a switching device that can close, carry and disconnect the current under normal circuit conditions and can close, carry and disconnect the current under abnormal circuit conditions within a specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The division of high-voltage and low-voltage boundaries is relatively vague. Generally, those above 3KV are called high-voltage appliances.

The circuit breaker can be used to distribute electric energy, start the asynchronous motor infrequently, protect the power line and motor, and automatically cut off the circuit in case of serious overload, short circuit, undervoltage and other faults. Its function is equivalent to the combination of fuse switch and over and under heating relay. Moreover, it is generally not necessary to change the parts after breaking the fault current. At present, it has been widely used.

Power distribution is an extremely important link in the generation, transmission and use of electricity. The distribution system includes transformers and various high and low voltage electrical equipment, and the low voltage circuit breaker is an electrical appliance with large amount and wide range.